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How to creat function to call eg int function1(int, ...)

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  How to creat function to call eg int function1(int, ...) Angus <anguscomber@gmail.com> - 2011-08-12 11:58 -0700
    Re: How to creat function to call eg int function1(int, ...) Victor Bazarov <v.bazarov@comcast.invalid> - 2011-08-12 15:22 -0400
      Re: How to creat function to call eg int function1(int, ...) Juha Nieminen <nospam@thanks.invalid> - 2011-08-14 18:18 +0000
        Re: How to creat function to call eg int function1(int, ...) Victor Bazarov <v.bazarov@comcast.invalid> - 2011-08-15 08:50 -0400
          Re: How to creat function to call eg int function1(int, ...) Juha Nieminen <nospam@thanks.invalid> - 2011-08-15 13:33 +0000
            Re: How to creat function to call eg int function1(int, ...) SG <s.gesemann@gmail.com> - 2011-08-15 06:41 -0700
            Re: How to creat function to call eg int function1(int, ...) Nobody <nobody@nowhere.com> - 2011-08-15 19:25 +0100
              Re: How to creat function to call eg int function1(int, ...) Juha Nieminen <nospam@thanks.invalid> - 2011-08-16 07:36 +0000
    Re: How to creat function to call eg int function1(int, ...) "Alf P. Steinbach" <alf.p.steinbach:usenet@gmail.com> - 2011-08-12 21:35 +0200

#8740 — How to creat function to call eg int function1(int, ...)

Hi

I need to put all functions calling into a C API into a separate
source file unit.  It is due to defines interfering with other code.
So to keep the possibly interfering code separate.

Anyway, most functions are eg int function2(int) so I just implement
in separate file like this:
int XXfunction1(int val) { return function(val) }

But I also have functions with variable arguments like this: extern
int function2(int, ...)

So how can I write my own function which calls that?

This doesn't seem to work:
int XXFunction2(int val, ...) {
   return function2(val, ...);
}

How do I write the function?

Angus

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#8745

On 8/12/2011 2:58 PM, Angus wrote:
> I need to put all functions calling into a C API into a separate
> source file unit.  It is due to defines interfering with other code.
> So to keep the possibly interfering code separate.
>
> Anyway, most functions are eg int function2(int) so I just implement
> in separate file like this:
> int XXfunction1(int val) { return function(val) }
                                                  ;
>
> But I also have functions with variable arguments like this: extern
> int function2(int, ...)
>
> So how can I write my own function which calls that?
>
> This doesn't seem to work:
> int XXFunction2(int val, ...) {
>     return function2(val, ...);
> }
>
> How do I write the function?

There is no portable way.  Some compilers would let you call that 
function with 'va_list' instead of the arguments.  Consult your compiler 
documentation or post to the newsgroup for your compiler.

V
-- 
I do not respond to top-posted replies, please don't ask

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#8842

Victor Bazarov <v.bazarov@comcast.invalid> wrote:
> There is no portable way.  Some compilers would let you call that 
> function with 'va_list' instead of the arguments.  Consult your compiler 
> documentation or post to the newsgroup for your compiler.

  Since when is the C89 standard (and hence by extension the C++98 standard)
not portable?

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#8857

On 8/14/2011 2:18 PM, Juha Nieminen wrote:
> Victor Bazarov<v.bazarov@comcast.invalid>  wrote:
>> There is no portable way.  Some compilers would let you call that
>> function with 'va_list' instead of the arguments.  Consult your compiler
>> documentation or post to the newsgroup for your compiler.
>
>    Since when is the C89 standard (and hence by extension the C++98 standard)
> not portable?

WTF are you talking about?  I, for one, am tired of your riddles.  Be 
verbose.  I have no intention of guessing what you mean.

V
-- 
I do not respond to top-posted replies, please don't ask

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#8861

Victor Bazarov <v.bazarov@comcast.invalid> wrote:
> On 8/14/2011 2:18 PM, Juha Nieminen wrote:
>> Victor Bazarov<v.bazarov@comcast.invalid>  wrote:
>>> There is no portable way.  Some compilers would let you call that
>>> function with 'va_list' instead of the arguments.  Consult your compiler
>>> documentation or post to the newsgroup for your compiler.
>>
>>    Since when is the C89 standard (and hence by extension the C++98 standard)
>> not portable?
> 
> WTF are you talking about?  I, for one, am tired of your riddles.  Be 
> verbose.  I have no intention of guessing what you mean.

  va_list is part of the C89 standard, yet you claim there is no portable
way.

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#8862

On 15 Aug., 15:33, Juha Nieminen wrote:
>
> va_list is part of the C89 standard, yet you claim there is
> no portable way.

I fail to see a contradiction here.
Maybe you did not understand what this thread is about.

--
SG

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#8871

On Mon, 15 Aug 2011 13:33:45 +0000, Juha Nieminen wrote:

>   va_list is part of the C89 standard, yet you claim there is no portable
> way.

Read the original question:

> But I also have functions with variable arguments like this:
> extern int function2(int, ...)
> 
> So how can I write my own function which calls that?

To which, the answer is "there is no portable solution". If the OP was
writing the function, he could just write a va_list based version. But if
all he has is a variadic function, there's no portable way to "wrap" it
(i.e. write a function which is itself variadic and which passes those
arguments down to the original function).

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#8889

Nobody <nobody@nowhere.com> wrote:
> On Mon, 15 Aug 2011 13:33:45 +0000, Juha Nieminen wrote:
> 
>>   va_list is part of the C89 standard, yet you claim there is no portable
>> way.
> 
> Read the original question:
> 
>> But I also have functions with variable arguments like this:
>> extern int function2(int, ...)
>> 
>> So how can I write my own function which calls that?
> 
> To which, the answer is "there is no portable solution". If the OP was
> writing the function, he could just write a va_list based version. But if
> all he has is a variadic function, there's no portable way to "wrap" it
> (i.e. write a function which is itself variadic and which passes those
> arguments down to the original function).

  I see. I thought the original question was how to pass a variable number
of arguments from one function (taking them) to another (also taking them),
for which there is indeed a standard solution.

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#8746

On 12.08.2011 20:58, Angus wrote:
>
> I need to put all functions calling into a C API into a separate
> source file unit.  It is due to defines interfering with other code.
> So to keep the possibly interfering code separate.
>
> Anyway, most functions are eg int function2(int) so I just implement
> in separate file like this:
> int XXfunction1(int val) { return function(val) }
>
> But I also have functions with variable arguments like this: extern
> int function2(int, ...)
>
> So how can I write my own function which calls that?
>
> This doesn't seem to work:
> int XXFunction2(int val, ...) {
>     return function2(val, ...);
> }
>
> How do I write the function?

In some cases, such as with printf family, you can find variants that 
accept va_list. Then just use the standard library's macros.

Otherwise, you need to find a way to express a general call as a 
sequence of calls with known arguments. That depends entirely on the 
function. Maybe you need to single out the important use-cases.

The way standard iostreams do this can serve as main example of a 
reasonable way to do it, but iostreams rely on the fact that arguments 
are processed in sequence, which your function may not necessarily do.


Cheers & hth.,

- Alf

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